1// Copyright 2012 Google Inc. All Rights Reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15package main
16
17import (
18	"bufio"
19	"errors"
20	"fmt"
21	"net"
22	"net/url"
23	"os"
24	"os/exec"
25	"strings"
26	"syscall"
27	"time"
28)
29
30type Client struct {
31	ProxyBin string
32	Args     []string
33
34	insecure bool
35}
36
37func (c *Client) Run() error {
38	if err := c.resolveArgs(); err != nil {
39		return fmt.Errorf("resolveArgs() got error: %v", err)
40	}
41
42	// Connect to the proxy.
43	uconn, hconn, addr, err := c.connect()
44	if err != nil {
45		return fmt.Errorf("connect() got error: %v", err)
46	}
47	// Keep the unix socket connection open for the duration of the request.
48	defer uconn.Close()
49	// Keep a connection to the HTTP server open, so no other user can
50	// bind on the same address so long as the process is running.
51	defer hconn.Close()
52
53	// Start the git-remote-http subprocess.
54	cargs := []string{"-c", fmt.Sprintf("http.proxy=%v", addr), "remote-http"}
55	cargs = append(cargs, c.Args...)
56	cmd := exec.Command("git", cargs...)
57
58	for _, v := range os.Environ() {
59		if !strings.HasPrefix(v, "GIT_PERSISTENT_HTTPS_SECURE=") {
60			cmd.Env = append(cmd.Env, v)
61		}
62	}
63	// Set the GIT_PERSISTENT_HTTPS_SECURE environment variable when
64	// the proxy is using a SSL connection.  This allows credential helpers
65	// to identify secure proxy connections, despite being passed an HTTP
66	// scheme.
67	if !c.insecure {
68		cmd.Env = append(cmd.Env, "GIT_PERSISTENT_HTTPS_SECURE=1")
69	}
70
71	cmd.Stdin = os.Stdin
72	cmd.Stdout = os.Stdout
73	cmd.Stderr = os.Stderr
74	if err := cmd.Run(); err != nil {
75		if eerr, ok := err.(*exec.ExitError); ok {
76			if stat, ok := eerr.ProcessState.Sys().(syscall.WaitStatus); ok && stat.ExitStatus() != 0 {
77				os.Exit(stat.ExitStatus())
78			}
79		}
80		return fmt.Errorf("git-remote-http subprocess got error: %v", err)
81	}
82	return nil
83}
84
85func (c *Client) connect() (uconn net.Conn, hconn net.Conn, addr string, err error) {
86	uconn, err = DefaultSocket.Dial()
87	if err != nil {
88		if e, ok := err.(*net.OpError); ok && (os.IsNotExist(e.Err) || e.Err == syscall.ECONNREFUSED) {
89			if err = c.startProxy(); err == nil {
90				uconn, err = DefaultSocket.Dial()
91			}
92		}
93		if err != nil {
94			return
95		}
96	}
97
98	if addr, err = c.readAddr(uconn); err != nil {
99		return
100	}
101
102	// Open a tcp connection to the proxy.
103	if hconn, err = net.Dial("tcp", addr); err != nil {
104		return
105	}
106
107	// Verify the address hasn't changed ownership.
108	var addr2 string
109	if addr2, err = c.readAddr(uconn); err != nil {
110		return
111	} else if addr != addr2 {
112		err = fmt.Errorf("address changed after connect. got %q, want %q", addr2, addr)
113		return
114	}
115	return
116}
117
118func (c *Client) readAddr(conn net.Conn) (string, error) {
119	conn.SetDeadline(time.Now().Add(5 * time.Second))
120	data := make([]byte, 100)
121	n, err := conn.Read(data)
122	if err != nil {
123		return "", fmt.Errorf("error reading unix socket: %v", err)
124	} else if n == 0 {
125		return "", errors.New("empty data response")
126	}
127	conn.Write([]byte{1}) // Ack
128
129	var addr string
130	if addrs := strings.Split(string(data[:n]), "\n"); len(addrs) != 2 {
131		return "", fmt.Errorf("got %q, wanted 2 addresses", data[:n])
132	} else if c.insecure {
133		addr = addrs[1]
134	} else {
135		addr = addrs[0]
136	}
137	return addr, nil
138}
139
140func (c *Client) startProxy() error {
141	cmd := exec.Command(c.ProxyBin)
142	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
143	stdout, err := cmd.StdoutPipe()
144	if err != nil {
145		return err
146	}
147	defer stdout.Close()
148	if err := cmd.Start(); err != nil {
149		return err
150	}
151	result := make(chan error)
152	go func() {
153		bytes, _, err := bufio.NewReader(stdout).ReadLine()
154		if line := string(bytes); err == nil && line != "OK" {
155			err = fmt.Errorf("proxy returned %q, want \"OK\"", line)
156		}
157		result <- err
158	}()
159	select {
160	case err := <-result:
161		return err
162	case <-time.After(5 * time.Second):
163		return errors.New("timeout waiting for proxy to start")
164	}
165	panic("not reachable")
166}
167
168func (c *Client) resolveArgs() error {
169	if nargs := len(c.Args); nargs == 0 {
170		return errors.New("remote needed")
171	} else if nargs > 2 {
172		return fmt.Errorf("want at most 2 args, got %v", c.Args)
173	}
174
175	// Rewrite the url scheme to be http.
176	idx := len(c.Args) - 1
177	rawurl := c.Args[idx]
178	rurl, err := url.Parse(rawurl)
179	if err != nil {
180		return fmt.Errorf("invalid remote: %v", err)
181	}
182	c.insecure = rurl.Scheme == "persistent-http"
183	rurl.Scheme = "http"
184	c.Args[idx] = rurl.String()
185	if idx != 0 && c.Args[0] == rawurl {
186		c.Args[0] = c.Args[idx]
187	}
188	return nil
189}
190